Variation in phenotype (mutants!)

Obviously, variation in traits is present in all populations and all species, but its quite easy to forget that – a mallard looks like a mallard, right? Evolution acts upon this variation, be it timing of flowering, anti-predator behavior or body size, constantly. I find variation in “characteristic” traits very interesting (and by “characteristic”, I mean how a naturalist would recognize a species, for instance in plants this might be color, growth form, leaf shape, etc.). I’ve been noting these for quite awhile and keeping a photo log – mostly of flower color, which is especially interesting to me – here’s a selection.

This isn’t meant as a real ecology post, just an appreciation for the natural world, but do bear in mind the little tidbits of science thrown in – they’ll only make it more interesting. As Huxley famously said, “To the person uninstructed in natural history, his country or sea-side stroll is a walk through a gallery filled with wonderful works of art, nine-tenths of which have their faces turned to the wall.”

I’ll mostly put a “normal” picture first and then the mutant. Here’s a normal Mimulus guttatus, the common yellow monkeyflower – a widespread, common and lovely species.

McLaughlin Reserve, Lake County, CA. 
And a weird red mutant:

McLaughlin Reserve, Lake County, CA

A normal Tritelia laxa.

Berryessa-Knoxville Rd., Napa County, CA

And a white one:

Berryessa-Knoxville Rd., Napa County, CA

A normal blue-eyed “grass” (really an iris), Sisyrinchium bellum:

McLaughlin Reserve, Lake County, CA

and a white one:

McLaughlin Reserve, Lake County, CA

Normal Mimulus nudatus, a cool serpentine endemic in the northern coast range.

McLaughlin Reserve, Lake County, CA

And a weird beige morph:

McLaughlin Reserve, Lake County, CA

And both normal and white morphs of Collinsia sparsiflora:

McLaughlin Reserve, Napa County, CA

Normal and white morphs of Mimulus layneae. Interestingly, the two white individuals in this population had flatter flowers as well.

McLaughlin Reserve, Lake County, CA

Why are white flowers so common in plants? Purple or reddish colors are caused by a group of chemicals called anthocyanins. These are synthesized in a pretty complex pathway that involves a bunch of steps, all mediated by proteins. If a mutation (or developmental issue), interrupts the function of any of these steps, you get a loss of function, which in this case becomes a white flower.

In some species, there is simply a polymorphism – its not rare to have differently-colored flowers (or -colored seed, or -shaped fruit, etc.). This Leptosiphon sp. has both pink and white flowers in roughly equal proportions in a population I looked at.

McLaughlin Reserve, Lake County, CA
Like Leptosiphon, many other members of the Polemoniaceae have white/colored polymorphisms within populations. Navarretia mellita (often a sandy plant!), is one:
McLaughlin Reserve, Lake County, CA

McLaughlin Reserve, Lake County, CA

Of course, color polymorphisms aren’t restricted to flowers, or even plants. A cool hypothesis to explain the existance of color polymorphisms in many species of raptors is that it is harder for prey to figure out what is a predator if they all look different. To the best of my knowledge, that hypothesis is still up for debate, but its clever and seems logical. Here is a pair of Variable Hawks, Buteo polyosoma:

Bosque del Pomac, Lambayeque, Peru
And another morph, of the same species!
A juvenile, I think. Bosque del Pomac, Lambayeque, Peru
I don’t know any hypotheses for the maintenance of color polymorphisms in caterpillars, but some have them. Hyles lineata feeding on Abronia villosa:
San Diego Co., CA

San Diego Co., CA

Data I’ll never publish: Antirrhinum herbivory

Inspired by this post, I’m going to try to put the results of small (but interesting) experiments up here every once and awhile. In the summer of 2014, I spent a lot of time washing plants. I was – and still am – curious of the function(s) of plant exudates. I primarily did this with Trichostema laxum and Atriplex rosea (in 2013), but I also did it with Mimulus layneae and Antirrhinum cornutum (California snapdragon). The snapdragon gave me interesting results.

(this post should also be regarded as potential project for someone else: I started it in May – there is plenty of time to get up to McLaughlin and do it again this year).

One of the experimental A. cornutum, showing leaf damage.

This snapdragon, while not as heavily glandular as Trichostema or that Mimulus, is fairly glandular-sticky, even entrapping a small number of minute insects (see the table/supplementary material). Under the microscope, you can see the fairly dense short glandular trichomes (the longer trichomes are mostly nonglandular) on the stalk and flower bud.

Stem of A cornutum with an entrapped insect.
Flower bud showing short glandular and long nonglandular trichomes.

Wondering whether the glandular exudate is defensive, I did an experiment where I removed it with water. Most glandular exudates in CA summer annuals seem water soluble, so a spray bottle rainfall takes off much of the exudate (observationally verified in situ with a 20x loupe – plus whatever was in this exudate made suds on the plant!). This manipulation was my first treatment group. Of course, adding water to a plant has an effect of its own, so I also had a water control group, where I added the same amount of water below the plant’s leaves, as to not wash off any exudates. Finally, I had a true control group, which received no water whatsoever. I instituted these treatments on the 30th of May and reapplied them on the 17th of June. Each time, I recorded the number of leaves, flowers, fruit, and plant height, as well as any damage. I also checked the plants, but did not reapply treatments on the 2nd and 19th of July (the last check all were senescent).

During the experiment, plants suffered two main forms of herbivory. The first type, which was most common and most destructive, was that the stems were entirely clipped off. I’m nearly positive this was by jackrabbits (indicated by a single flat cut diagonally across the stem) and it usually killed the plant. The photos below shows what remained.

A killed experimental A. cornutum plant. See it?!? Its the little stem to the bottom left of the flag. Also notice a nice healthy Lessingia in the background. They, too, are extremely glandular and sticky.
A survivor of mammalian herbivory. If the meristem was not completely destroyed, they often came back and branched like this. Like the classic overcompensation “herbivore-plant mutualisms”, the resulting plants were often bigger than the others, with more reproductive structures, but unlike this “mutualism”, it was too late in the season and they had low fitness, as they could not mature these structures.

The mammalian herbivory was not random. Of the 25 plants per treatment, 11 in the control group, 13 in the rainfall simulation (exudate removal) and a whopping 20 in the water control group were eaten by mammals (this is nonlethal, lethally was 10, 12, 18). With a simple chi-squared test, we can demonstrate that this was likely nonrandom (X2 = 7.3688, df =2, p = 0.025) (for lethal, X2 = 5.5714, df=2, p = 0.062). Why were the mammals targetting the water control plants so heavily?

Were they bigger and thus easier to find or just more profitable to eat? They were not significantly different in height, fruit or flower numbers from the other two groups during any check. I don’t have data on plant quality (perhaps the less water-limited plants were more nutritious or something?).

The other type of damage was equally-interesting. Heliothis phloxiphaga is a generalist caterpillar on glandular plants. It was the primary herbivore on my columbines, as well as a common herbivore on Trichostema laxum and other sticky plants. Like most heliothiine noctuids, it feeds primarily (but not exclusively) on reproductive structures. I only observed it once on Antirrhinum (eating a fruit), but all the fruit damage I found was consistent with it (and that’s one more time than I saw a jackrabbit eat it!).

The other type of damage: caterpillar fruit predation.

I had hypothesized, that if the exudate were defensive, the washed plants would be most heavily eaten. This hypothesis was supported with the fruit damage. Rainfall plants received far more damage than the other groups. (note: I didn’t actually analyze this with zero-inflated binomial, as it should be. There is a problem, in that only 7/25 of the water control plants had any fruit at all because of the rabbits.)

A crumby excel graph of proportion fruits damaged.

What does this all mean? Obviously, it means that mammalian and insect herbivores are responding to different plant traits. What they are exactly, I’m not sure (especially for mammals). If anyone (nudge, nudge, wink, wink) were to repeat this experiment, with a larger sample size, and maybe some other mechanistic experiments (perhaps cage controls and lots more trait data to see what is different in the water control and rainfall manip groups), I think its a pretty good system that someone could get a paper – if not a few – out of.

Fire, transpiration, local hydrology and some very happy sunflowers

The Rocky fire swept through McLaughlin Reserve at the end of July. Nearly five weeks later, I resurveyed some sites that I went through the week after. The amount of life that had survived in the completely wrecked sites was astonishing, as was the quick resprouting of some plants (Rhamnus, Salix, Quercus, Vicia, Brassica, Asclepias, etc.). But the most surprising thing was the “winners” of the fire. I’ve walked columbine this seep many times a week during the past two summers. This time, I was struck by how large several serpentine sunflowers (Helianthus exilis) and tumbling orache (Atriplex rosea) had become.

Several stupendously super-sized serpentine sunflowers stoutly standing in foreground. A couple orache visible in the background.
Before the fire and all of last year, these were quite small plants, reaching maybe 1-2′ tall with a couple dozen flowers. In many places, they end at 6-10″ with just a few flowers. These plants were over 3′ tall and each had a hundred or more flowers. What happened?
Last year there was a little bit of odd late-summer weather, with a few overcast cooler days (it is usually above 90 and not a cloud in the sky here). On those days, one very small seep that I had a columbine population in would fill up a couple tiny puddles that hadn’t had water for months. After a couple times, I mentioned this to the reserve manager here and she pointed out that the plants around the seep don’t transpire as much on cloudy days, so the water being put out by the seep was not being used up before it got to the ground. 
What transpires less than plants in overcast conditions? Dead plants. Right after the Rocky Fire, the seep with the sunflowers was flowing again big time (it is much larger and had much denser vegetation around it than the one that I could see the changes before). The amount of water in this seep now is greater than it’s been since April or so. While the sunflowers and Atriplex are past the end of the visible water in the seep by a few dozen yards, it is still flowing belowground and these are pretty much the first plants that would be getting any of that water, as all plants upstream are fried.  
This section had been completely dry for months before the plants stopped sucking up all of the water flow. Also note all the greenery. That is resprouting of Aquilegia eximia, Stachys albens, Salix sp. and a few grasses and sedges (you can fire me as your naturalist if you’d like – I have no idea what species are here).  
This was an cool and unexpected – though completely logical – thing to find in the aftermath of the fire. I’m sure its been described before, but it was really eye-opening to me to see how much water those plants were transpiring and just how much influence this had on the hydrology and the success of other plants far below them (it seems like asymmetric resource competition – the manzanita and willows above were dictating the reproductive potential of the sunflowers below).
Something similar may have been happening to trigger this flowering of Mimulus guttatus, but I’m a bit puzzled, as this was in a strange location for that to occur and nothing else around it was doing particularly well. It was certainly a pleasant surprise to see some spring-like color at the end of the summer!
I’ll write a longer post about the Jerusalem fire (more lost experiments… but not all!) and some other interesting observations that I’ve had during my last couple days of wanderings. But I’ve got more field work to do now. 
Dragonflies were hanging out in the seep like nothing had changed. I believe this is Aeshna walkeri (common last year here and with the same gestalt), though I didn’t have my net with me to confirm and I wouldn’t have wanted to disturb her egg-laying anyway (I’m a bleeding heart when it comes to dragonflies… and snakes… and beetles… and others). 

Oops, my field site disappeared: lessons learned from the Rocky Fire

Last week, on the 29th, I was coming back in after a day in the field at the UC-Davis McLaughlin Reserve (in Lake County, CA) where I do all my work. I was setting up some insects in containers in the building when some one from next door came over to point out a smoke plume rising NW of the reserve.

I wonder if this is the first photo of the Rocky Fire… it was taken at either 4:01 PM, Cal Fire says it started at 3:29, a few miles NW of the reserve. 

Within a few minutes, it was obvious that this wasn’t going to be like the other, smaller fires that were put out quickly the week before in the same area. I continued doing my work and made dinner. I wasn’t particularly concerned, since the wind was pushing towards the fire and the plume was making its way away. By nightfall, it got worse, and the wind began to shift.

7:57 PM and the smoke plume still moving away from us.  

At this time, I went next door to the mining building to hang out with the safety guy there, who was on site in case this caused any problems for them. By 10ish, the power had gone out, the wind had come around and there was smoke and a small amount of ash falling. By 11, CalFire had shown up and told us it had jumped the road and that we were going to be evacuated soon. I packed up a few clothes, my bug nets, computer and a little bit of food and was on the road by midnight and back in Davis a little before 3 AM (nearly hitting a deer in the process). I fully expected to be back in a day or two. I had planned to stay there for a couple weeks – my longest continuous trip of the summer – as both the tarweeds and the columbines are in the middle of their season in late July/early August.

Navarretia mellita, the subject of one of my experiments, which was going along swimmingly before I left. 

After the evacuation and my near deer miss, I was running on a bit of adrenaline… I got to sleep by 4 AM or so and was up again by seven. And I spent the better part of the following week that I was evacuated refreshing the CalFire website as the fire grew in waves until nearly 70,000 acres (that is ~110 square miles). My sites all lay pretty much on the fire perimeter – I had no idea what to expect until I got back, as I knew that fires burned patchily.

Doing small-scale insect-plant interactions, I do my experiments on a plant-scale – manipulating traits of one plant, and I mostly work on annuals and all on a yearly basis (which means I can’t do a pre-/post-fire comparison). I do many experiments each season – this year I was running 7 at the time of the fire – all in the northern and western parts of the reserve, where the fire was most intense. So my heart was racing the whole trip back, when I was allowed in on Thursday (the 6th – over a week after evacuation). I dropped some refrigerated stuff off and quickly hurried out to my sites…

This is the wet meadow where my recently published experiment took place and where I had another experiment going this year. 

As I drove in to my columbine experiment, I knew it wasn’t going to be a pretty sight. You can still see a streambed on the left side. Surrounding it was a nice population of serpentine columbine (Aquilegia eximia), hedge-nettle (Stachys albens) and common monkeyflower (Mimulus guttatus) with a scattered coffeeberrry (Rhamnus sp.) and willow (Salix sp.), bordered by THICK chaparral (manzanitas, oaks, chamise, etc.). I did find remnants of the experiment…

I should have bought the pin flags rated for raging-wildfire temperatures. Next time. 

My next experiment was through a tiny circuitous trail which I had carefully machete hacked earlier in the season through manzanita and cypress. It involved going over and under a number of logs and around small breaks in the chaparral. Yesterday I could walk (and see) in a straight line through a whole lot of nothing. All I found was a tiny bit of melted flagging tape, attached to a columbine stalk that had somehow escaped total incineration…

Based on its location (and most of my landmark shrubs were gone), I think this was control #50. It formerly was under a manzanita. I found it in the middle of a large, barren field.  

All was not lost, however! My next project was a huge set of experiments examining defensive induction in a tarweed, Hemizonia congesta (this specific epitaph is accurate, at least for me). Fire fighters had made a dozer line through the upper end of this field between two roads. The flames reached the two roads and the firebreak, but fortunately never jumped and my site (containing 250 plants which I had been following for months), ~200 meters beyond, remained intact. I was a bit worried that perhaps the insects would have been affected, but the insect communities seemed normal in abundance and identity.

My site is on the middle hump in the mid-ground. You can see the sparse vegetation on those serpentine barrens compared to the field of Avena in the non-serpentine areas. 

The grasslands were wild to walk around. Grass fires don’t burn as hot nor for as long as chaparral fires, so some things survived. Not among those surviving were the rabbit-poop looking burnt star thistle flowers and fruit.
 

It burned the spines right off the thistle flowers. And it looked like most hadn’t seeded… hooray!
The living stuff on the right is a variety of tarweeds (Hemizonia, Holocarpha and Calycedinia spp.) growing on a serpentine barren (low biomass). The burned area on the left was Avena and star thistle and had much higher biomass and apparently burns better. 
Like the wicked witch of the west when confronted with water, milkweeds (this is Asclepias eriocarpa) apparently just melt in the face of fire. 

Not all the milkeeds melted, fortunately for this large monarch caterpillar (and the orange oleander aphids out of focus in the foreground). There were a bunch on a small surviving patch of Asclepias fascicularis which was no more than 2 meters from completely scorched earth. I wonder whether they emigrated here from melted plants or if they were all on the one patch to begin with.

The grassy areas had tons of Mourning Doves. More than I’ve ever seen at one time in my life. Did they group up after the fire and emigrate right to my field site? I don’t have a clue. I usually see them near Croton (Eremocarpus) setigerus, but that’s not around this site – I wonder if they were eating burned thistle heads or other seeds exposed by the burning of all the grass.

The patchiness of the fire on a microscale was crazy. Here a small patch of seeding Mimulus nudatus (a rare California endemic found only in serpentine soils in a small part of the northern coast range) stands amidst a scorched landscape. 

Another set of experiments I had were also very close to a burned area, but they too, were spared. I was studying the ecology of two sticky species: Navarretia mellita and Madia elegans. Both are weedy species that love disturbance. There is an old road above the center that is drive-able, but rarely driven and hosts nice populations of both species that like the roadside disturbance. The Navarretia experiment was pretty much fine, being about 5 yards from the road. In the couple weeks that I hadn’t checked it, some of the seeds had dehisced, but I had final inflorescence number for all the plants, which is enough of a fitness proxy for my purposes.

Big flags, little tiny plants.

The tarweed (Madia elegans), on the other hand, suffered a little bit. During the fire, trucks must have driven by that site hundreds and hundreds of times… I was there for the afternoon yesterday and had 4 or 5 cars drive by twice each (it is a dead-end) – and that was long after the fire was out in that section. Tarweeds are sticky and I was manipulating the amount of insects they caught (following up on Billy and Ian’s Madia study and my columbine study). Most of the plants were within a yard of the road edge (non were on the road – none got hit), but with the hundreds of vehicle passes the amount of dirt kicked up and subsequently caught by the tarweeds was crazy. The treatments – varying amounts of dead fruit flies – were sort-of intact, but redoing the treatments was a major trial, as the fruit flies wouldn’t stick. This will get better as they grow and they ought to flower for another month or so, so perhaps this won’t be a complete wash… we’ll see.

Its hard to see in this picture, but pretty much every glandular trichome on the plant had dust stuck to it, rendering it pretty much completely unsticky. 

The last experiment, a manzanita fruit manipulation, had pretty much been doomed from the get-go. I started the experiment early in the season, when the plants thought they had lots of water, but soon after, they aborted all the fruit I had in the experiment. So I moved to a new site, on the edge of a pond, where the shrubs were a little bit happier, but I started it too late (as I was still nursing the first try along a little bit). The fire left only one of those manzanitas standing at all as it whipped around the pond. Not a huge loss, though it would have been nice to get the last set of data.

A dead deer in the pond that the manzanitas were next to. I don’t know for sure that this was fire related, but it seems likely as the chaparral up to this pond on three sides was burned completely for hundreds and hundreds of meters. 

 In the pond, besides the dead deer pictured above, life seemed to go on fine. The tule and cattails were intact, as good, water-filled greenery should be. Pied-billed grebes continued to feed streaky little babies and coot made all their funny noises. I finally saw the first Ruddy Duck baby of the year – in years past there have been quite a few in this pond and this year there were quite a few pairs, but only one duckling seems to have come out. A Gadwall nest that I found a few weeks back should have hatched (or been preyed upon by coyotes, raccoons, etc., by now) and a few rather large babies were around the pond, along with the first Green-winged Teal of the season. Tiger beetles ran on the shores and dragonflies flitted by, as if nothing had happened.

I’m not sure where this jackrabbit fled during the fire, but he’s a survivor for sure – there wasn’t much unparched in the area that I found him. There were a good number of these around – and strikingly, in a lone patch of Garrya, with literally nothing for hundreds of yards around, a chipmunk scolded me!
Other folks lost experiments as well. This was a bird exclosure, under which was a chamise that had been monitored for years. 

The amount of life around, even in burned areas just a week later was astounding. While exploring, I heard a pair of Rufous-Crowned Sparrows chipping from a couple mostly demolished manzanitas along a completely devegetated streambed. They popped out to check me out – I suspect that most territorial animals are dealing with a lot of stragglers coming by. I had a secondhand report of a mountain lion wandering down a road near fire crews in the middle of the day – not a typical behavior. While watching sandpipers, I heard a barking, like that of a large dog coming from near where my truck was parked. Thinking it might be a lost dog displaced by the fire, I headed towards it. As I neared the truck, on a rock above it was a coyote, looking down at me and barking like hell. As I fumbled in my backpack for my camera, he ducked behind the rock and continued berating me until I left.

Walking through dense manzanita chaparral is miserable. Walking through the same area now is quite easy.

Though it makes you quite dirty. This was after only about 10 minutes. After an afternoon of hiking around, I looked like a coal miner.

For a number of reasons, I spend a bit of time looking at spiders: they are important predators on many plants, I’ve worked on crab spider behavior, and much of the Bahamian island research revolves around them. One of the first signs of life in the fire area was funnel web spider (Agelenidae) webs, which are a thick mat of webbing with hole the size of a nickel or so (like a funnel, as the name suggests). There were tons of them on top of the blacked dirt and vegetation.

A nice clean, fresh, funnel web on top of blackened soil. 

In contrast, in non-burned areas, the webs were messy with ash that was clearly flying in large quantities with the fire nearby. I wondered why the spiders hadn’t spun a new web or cleaned it out. I suspect that the reason has to do with how costly spider silk is to the spider. Being made of protein and laid out carefully, it is both nutritionally costly and time-intensive to make a web. Many spiders eat their webs if they take them down and there is even a group of parasitic spiders which eat the webs that other spiders make (!!!).

A web with lots of entrapped ash. I think it is a theridiid, but I didn’t look too closely. All the webs were covered like this.
Pocket gophers also survived, with fresh diggings in the 5 or so days since the fire passed through this area. I just saw my first pocket gopher a few weeks ago, while being acquainted with their diggings for years. They have really, really weird ears.

Its been a really interesting time to look at the natural history of this area. The next few years, while I continue my phd, will also be an interesting time of watching fire-following plants, resprouters and who knows what else.

The fire opened up previously hidden scenes from dense chaparral, like this midden. I guess this was from when there was a nearby shale quarry operating, but I’m not sure. Those beer cans look old…

AND THEN…

I wrote most of this the night of 8/8/15. About 4 PM today (8/9/15), another call came on the radio about a smoke plume. I hurried outside and shit… another BIG fire, within a couple miles, this time SW of the station. This one has been termed the Jerusalem fire. I hurried and collected some seeds for a friend and reconned some badly dozered sections in the SE portion of the reserve.

Jerusalem fire, ~4:30 PM, 8/9/15. If the twittosphere is to be believed, those two plumes are from two separate arson fires.
These dozer lines are ridiculous. There are at least 4  (and a road) between this particular one and anywhere the Rocky fire actually burned. They tore the shit out of some really nice oak woodland habitat and compacted soil, etc. 
Fire haze does produce extremely beautiful light.

This charred live oak (?) leaf was one of many which rained down during my hike… the fire was 3-5 miles away at this point.

Like ecologists, firefighters seem to like to put flagging tape on anything interesting. Here on abandoned machinery. Its also on gates, fences, various poles, etc. 

A constant part of the wildlife now, these big birds are really thirsty, sometimes drinking 3,000 gallons every few minutes. I’m getting better at my identification of these. I think this is a Boeing 234 “Chinook”, but these two rotor helicopters seem almost as confusing as empid flycatchers… field guide.here

We’ll see how this one pans out… I’m not particularly worried for my experiments now. If they burn, they burn but there is a lot of burned area between this one and them (it is continuous, but the fire would need to turn a couple different ways before it got to anything).

The pond this CH-47 just refilled from is part of the complex where the field component of this paper took place. 

I did learn some field season lessons, as well.

Things I will do differently next summer:

1) Space my experiments out farther! The farther apart they are, the more likely a fire line will go between them in case something like this happens again.
2) Put them a little farther back from roads (this also would protect against accidental drive-overs).
3) Put them in a matrix of previously burned areas. Its hard to reburn the same areas two years in a row (though the Wragg fire managed that this year in Yolo/Solano counties!). That will allow a little extra safety.

And finally – while I lost some work (a couple months on a couple projects), I’ll certainly be able to repeat those next year and I’ll get a couple completed experiments from the seaon. Thankfully, I didn’t lose my house, my pets, my vehicles or my livelihood – others did.

A lone manzanita looks out over a burned land. The road you can see in the back right is Roundtop road, in Knoxville Recreation area. It would be a good place to check this out from (but do not, under any circumstances, camp in the campground there). I guess the area to the right all has already/will burn in the Jerusalem fire, too. 

Beginning research: floral polymorphisms in Trichostema laxum

The first steps of any research project are, for me, the most exciting. Therefore, I’ll write a quick post on something I’ve been spending a bit of time on. Last summer, I spent most of the summer trying to wash off chemical defenses on leaves. One plant I chose was Trichostema laxum – a mint endemic to California (it may occur in extreme southern Oregon, too) that occurs pretty commonly on dry serpentine streambeds at my field site in Lake/Napa counties. I’ve already written a quick post mentioning this plant, but I know a LOT more now!

Trichostema laxum, October 2014, McLaughlin Reserve, Napa County. Notice the position of the stigma in relation to the anthers – the style (the stigma’s tube) projects well beyond the anthers. This is the “normal” morph of the plant, referenced in the literature and seen in all herbarium specimens I’ve looked at so far.

While the herbivory and exudate stuff awaits analysis (a dissertation proposal will force me to do that soon!), I discovered the aforementioned flower color polymorphism and took a bunch of baseline data on it, which may be important in the coming months. The flower color polymorphism interests me most because of one population which had a high (~3%) proportion of the white/purple morph – no others had it. Was it just a random neutral mutation that didn’t drift out? If not – how is it maintained?

The four polymorphs of flower color. All from summer 2015, McLaughlin Reserve, Napa/Lake Counties.

The first question was, do the various flower colors differ in fitness from the normal (purple) morph? Trichostema laxum along with most other annual plants in California grasslands and serpentine barrens, is extremely variable in size depending on the microclimatic conditions. Within a population, some individuals can have three orders of magnitude more flowers than others (~10 to ~10,000). I found one small bush-sized individual (probably nearly a meter square) on a gopher mound – clearly the gopher had changed the nutrients or hydrology of that specific location favorably! Therefore, I compared polymorphs to their nearest neighbor of the normal morph, in an attempt to minimize this variability. This was a coarse test (without a huge amount of power), but I found no differences, though large variability among individuals. I will – hopefully – be able to confirm this in the laboratory rather easily. I took a good amount of pollinator data – which also awaits analysis.

A pink morph just barely open (though the stigma is open, so maybe its deformed?).  McLaughlin Reserve, Lake County, CA. 

The next logical step in the investigation was to grow plants in the lab and find out whether the color polymorphisms were heritable – an important consideration in any investigation relating to population-level polymorphisms. Trichostema have a reputation for being a tough genus to grow, in fact, a professor at Davis told me a former grad student planned a project on them, but couldn’t get any germination. I’ve been more fortunate (with help from Danny Barney at the USDA) and got decent germination with a rather simple protocol – laxum may be less picky than its relatives. I grew them all fall – they flowered in November and early December.

One of the first individuals in the lab. Isn’t it cute?

When I started looking closely at the plants in the lab, I found two more polymorphisms. The first was the lower lip patterning. In normal plants, the lower lip – and sometimes the next lowest two petals, have some purple splotches on them. This is likely a nectar guide, leading pollinators to the reward (and often only visible/really cool in the UV). I knew in the field that the completely white morph lacked a nectar guide as it lacks anthocyanin, the red/purple pigment in most plants, completely, so a purple nectar guide would be precluded. But I was surprised to see a purple flowered plant lacking it.

Clean purple lower lip. December 2014, in lab. 

While interesting, this was only found in one plant (though I have seeds of it now). Another polymorphism was also obvious in the captive plants and it solved one of my summer mysteries. During the summer, I wanted to do crosses with the various colored flowers. I didn’t think it would be that hard – an older paper reported that T. laxum was non-selfing and covered plants produced no seed. So I placed pollinator exclosures over a bunch of plants and did crosses by moving pollen from one plant to another. I then covered the plants again, letting them naturally set seed and figuring that the only seed I’d get would be that of the crosses. I pollinated ~10 flowers per plant and since mints have only 4 ovaries per flower, I figured I could get about 40 seeds a plant (probably 30 since my fine motor skills aren’t all that great). When I uncaged the plants and collected the seeds in October, I got quite a surprise – large numbers of seeds. Though not a full complement from any plant (there are MANY reasons for this besides lack of pollen), I got way too many seeds to have been either 1) my pollination, or 2) occasional lapses in the pollinator exclosures. Clearly the plants were self-pollinating somehow.

And here is the solution to the mystery! Where is the stigma? Its pretty much in the middle of the anthers. This one isn’t quite mature yet, but instead of opening after growing far past the anthers (see the first picture), it will open either right in the anthers or ever so slightly beyond. McLaughlin Reserve, Lake County, CA.

Looking closely at the individuals in the lab revealed the reason for this mystery. Some plants, like the first picture in this post, had long styles, which projected the stigma far past the anthers. Others, like the one above, had short styles and the stigma was amidst, or ever so slightly past the anthers. This proximity (I think) allows the plant to self pollinating either directly, or with the slightest bit of wind or insect movement (the “self-pollinating” morph. In the lab, more than half the plants developed into the self-pollinating morph, and while I hadn’t noted it during the season, I was able to go back to the hundreds of pictures I took and found pictures of it in the field. Strangely, they are not in the same proportion – my pictures are primarily of the “normal” variety – which accords with the one paper on the plant, as well as descriptions. I then examined the specimens in the herbarium, all of which were the “normal” morph (and purple, with patterned lower lips). Whether the lab creates the right environment for this morph to develop (whether there is a genetic propensity for it, or it is somewhat environmentally-driven) is unknown now, but I am working on it. Jenny Van Wyk – another grad student at Davis and extremely knowledgeable plant reproductive biologist – have quantified the differences between these morphs and found some really interesting correlates.

Flowers of the two morphs (self-pollinating, top; normal, below), at the same scale (lower lip broken in lower photo). 

Preliminarily – and our sample size is low as of now – the self-pollinating morph has larger flowers (corolla length, display height, style length), produces more pollen (300x more!) and has more, but more dilute, nectar. There is variability within morph, but so far, each plant has fit into one of the two morphs easily. How much this is an artifact of the laboratory setting is unclear, but photos of the self-pollinating morph and the pollinator-excluded plants producing seed point to something interesting happening in the field. Right now we are focused on the laboratory aspect, but we are considering experiments and observational data to be performed/gathered this upcoming year. We’d love to hear what anyone thinks of the system and interesting questions we can ask with it!

I’ll have some photos and interesting observations from my three-week trip to Chile soon, too. Lots of interesting botany, entomology and birdwatching (condors!).